Hydrogen sulfide (H2S), most commonly known as the source of the rotten egg odor, is now known to play important roles in mammalian cell signaling. These include regulation of vascular smooth muscle tone, neuronal activity, liver bile production and general cell protection from the oxidative stress of aerobic metabolism. Because of the potential toxicity of H2S, its cellular/organismal concentration is tightly regulated by enzymatic production and consumption pathways so that toxic levels are not reached. However, too little H2S, equivalent to too little reducing power and consequently too much oxidative stress, has been linked to numerous degenerative pathologies such as cardiovascular disease, rheumatoid arthritis, Alzheimer's type dementia, various cancers, and aging in general. Many of these and other pathologies result from the accumulation of cellular oxidative damage that, as is now known from numerous studies, could well be limited by antioxidants or reductants such as vitamins E, B and C and the beneficial phytochemicals associated with fresh vegetables and fruit, as well as H2S.
One way in which H2S may achieve these beneficial effects is by acting as a global cellular and organismal reductant, capable of shifting the cellular reductive/oxidative (redox) balance towards the reduced state and protecting against oxidative damage. Major sites of cellular oxidative damage include thiol groups on proteins, represented as PROTEIN-SH, or RSH where R is the protein. Protein thiols can become oxidized and linked as dithiol bonds (RS—SR), or bound to nitric oxide, NO, as RSNO, both of which can dramatically limit protein function and hence normal cellular activity. H2S along with other cellular reductants such as glutathione serve to reduce protein dithiols, or RSNOs, to reestablish protein function. Most cellular reductants are larger molecules compared to H2S and therefore cannot diffuse as rapidly, readily pass through cell membranes, or fit into smaller molecular spaces where some oxidized thiols occur. Therefore H2S may be one of the most important cellular defenses against oxidative stress.
H2S is regularly produced by human cellular metabolism, and can be augmented by dietary components that provide substrates for H2S-producing metabolic pathways. H2S production can also be augmented by the important but underutilized and understudied method of bathing in warm sulfur mineral springs, termed sulfur balneotherapy. Sulfur mineral springs are often highly valued for their healing qualities, most likely as a result of significant levels of H2S that are absorbed through the skin to help recharge cellular redox status. Scientific investigations of the effects of warm sulfur mineral springs are beginning to be published demonstrating benefits in a number of pathologies including cardiovascular degeneration, skin ailments, wounds, breathing difficulties, rheumatoid arthritis, hepatic, gall bladder and kidney diseases, metabolic and urological disorders, insomnia, and neurological deterioration. Although the chemistry of some sulfur mineral bath water is published and/or otherwise available, some commercial mineral springs still advertise an absence of the sulfur odor reflecting little understanding among mineral spring/therapeutic spa providers of the recently published beneficial effects of H2S.
The short and long term preservation of living biological material such as cultured cells, stem cells, and whole organs is essential for the use of this material in research and clinical applications such as transplantation. Preservation solutions and methods are designed to limit oxidative damage and loss of viability. Although H2S is produced endogenously, serving to protect cellular redox balance, compromised redox regulatory pathways in isolated cells or organs can be augmented by the exogenous addition of H2S. A sulfide bath designed to expose biological material to specific H2S concentration during preservation procedures could be used to enhance the viability of preserved samples.